Image forming apparatus

ABSTRACT

An image forming apparatus has a photosensitive drum configured to bear a developer image, a developing apparatus having a developing roller that bears developer and a developing blade that regulates the amount of the developer on the developing roller, and a detection portion that detects information on the amount of the developer stored in the developing apparatus. The image forming apparatus performs a discharging operation for discharging a coating agent, applied to a developing roller in an unused state, from the developing apparatus to the photosensitive drum, while varying an operational condition for the discharging operation varied based on the information.

This application is a continuation of application Ser. No. 15/176,450,filed Jun. 8, 2016.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an image forming apparatus.

Description of the Related Art

In image forming apparatuses such as printers which use anelectrophotographic image forming system (electrophotographic process),image recording is performed in the following manner: anelectrophotographic photosensitive member (hereinafter referred to as a“photosensitive member”) serving as an image bearing member is uniformlycharged; the charged photosensitive member is selectively exposed toform an electrostatic image on the photosensitive member; theelectrostatic image formed on the photosensitive member is visualized asa toner image using toner in developer; then, the toner image formed onthe photosensitive member is transferred to a recording material such asa recording sheet or a plastic sheet; and the toner image transferred tothe recording material is further heated and pressurized so as to befixed onto the recording material.

Such an image forming apparatus generally needs refilling of developerand maintenance of various process means. To facilitate the developerrefilling operation and the maintenance of the various process means, atechnique has been put to practical use in which the photosensitivemember, charging member, developing means, cleaning means, and the likeare collectively stored in a frame member to form a process cartridgethat can be installed in and removed from the image forming apparatus.The process cartridge system enables the provision of an image formingapparatus with high usability.

In conventional developing apparatuses used for image formingapparatuses, a method of applying a coating agent (lubricant) to adeveloping roller (developer bearing member) in order to suppressturn-up of a regulating blade (developer regulating member) and toreduce a driving torque has been widely used. In Japanese PatentApplication Laid-open No. H2-298971, powder with the same polarity asthat of toner is used as a coating agent for the developing roller.Japanese Patent Application Laid-open No. H8-227212 proposes that, as acoating agent, the following be coated at least on a surface of thetoner supply roller (developer supply member): powder with no chargingcapability or powder that is charged with the same polarity as thedeveloper and that has a charging capability having an absolute valueequivalent to or smaller than the charging capability of the developer.On the other hand, a technique for conventional image formingapparatuses is widely known in which the developer is periodicallydischarged so as to be restrained from being degraded. Japanese PatentApplication Laid-open No. 2006-23327 indicates that, in order tosuppress degradation of the toner in the developer, an operation ofperiodically discharging the developer is performed such that tonerconsumption for each page is constant.

The situation described below may occur when a coating agent is used inthe manner of Japanese Patent Application Laid-open No. H2-298971 andJapanese Patent Application Laid-open No. H8-227212. During the latterhalf of life of the image forming apparatus, durability of the developeror durability of a developing roller or a developing blade is degradedto deteriorate charging characteristics of the toner. Then, an initialcoating agent remaining in a developing chamber may move to therecording material along with a toner image at the time of imageformation. The coating agent attached to the recording material mayappear as streaks on the image or streak-like fogging images on a blankportion of the paper. Thus, the coating agent initially applied to thedeveloping roller is desirably discharged to the outside of thedeveloping chamber quickly.

However, for such a discharging method and a discharge frequencyaccording to the related art as described in Japanese Patent ApplicationLaid-open No. 2006-23327, the coating agent may fail to be fullydischarged and remain in the developing chamber. When image formation isperformed with the coating agent remaining in the developing chamber,the durability of the developer may be deteriorated or the developingroller may be degraded to deteriorate the charging characteristics ofthe toner, causing the coating agent to move to the recording materialalong with the toner image. This may also result in abnormal images suchas streaks and fogged images.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a technique enabling areduction in movement of a coating agent, applied to a developer bearingmember, to a recording material along with a developer image.

To accomplish the object, an image forming apparatus according to thepresent invention comprises:

an image bearing member configured to bear a developer image;

a developing apparatus having a developer bearing member that bearsdeveloper and a regulating member that regulates an amount of thedeveloper on the developer bearing member;

a detection portion that detects the amount of the developer stored inthe developing apparatus; and

a control portion that performs a discharging operation for dischargingthe developer from the developing apparatus, apart from an image formingoperation,

wherein the developer bearing member bears a coating agent during anunused state, and

in the discharging operation, an amount of the developer discharged whena first amount of the developer stored is detected is larger than asecond amount of the developer discharged when a second amount of thedeveloper stored that is larger than the first amount of the developerstored is detected.

To accomplish the object, an image forming apparatus according to thepresent invention comprises:

a developing apparatus including a developer bearing member that bearsdeveloper and a regulating member that regulates an amount of thedeveloper borne by the developer bearing member and that charges thedeveloper; and

a detection portion that detects the amount of the developer stored inthe developing apparatus,

the image forming apparatus executing a discharging operation that isdifferent from an image forming operation of forming a developer imageon a recording material and that moves the developer from the developerbearing member to an image bearing member,

wherein a coating agent that is powder other than the developer isapplied to the developer bearing member during an unused state, and

the image forming apparatus comprises a control portion that varies anexecution frequency of the discharging operation so as to increase theexecution frequency of the discharging operation with respect to anexecution frequency of the image forming operation as the amount of thedeveloper detected by the detection portion decreases.

The present invention enables a reduction in movement of a coatingagent, applied to a developer bearing member, to a recording materialalong with a developer image.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of an image forming apparatusaccording to an embodiment;

FIG. 2 is a schematic sectional view of a process cartridge in theembodiment;

FIGS. 3A to 3C are schematic sectional views of a developing apparatusin the embodiment;

FIG. 4 is a flowchart of a discharging operation in Embodiment 1;

FIG. 5 is a flowchart of a discharging operation in Embodiment 2;

FIG. 6 is a flowchart of a discharging operation in Embodiment 3;

FIG. 7 is a flowchart of a discharging operation in Embodiment 4;

FIG. 8 is a table indicating results of comparative verification for theembodiment;

FIG. 9 is a graph indicating results of comparative verification for theembodiment; and

FIG. 10 is a diagram illustrating results for the embodiment.

DESCRIPTION OF THE EMBODIMENTS

The following provides a detailed exemplary explanation of embodimentsof this invention based on examples with reference to the drawings.However, the dimensions, materials, shapes and relative arrangement ofconstituent components described in the embodiments may be suitablymodified according the configuration and various conditions of theapparatus to which the invention is applied. Namely, the scope of thisinvention is not intended to be limited to the following embodiments.

EMBODIMENT

An electrophotographic image forming apparatus according to anembodiment of the present invention will be described. Using anelectrophotographic image forming system, the electrophotographic imageforming apparatus (hereinafter also referred to as the “image formingapparatus”) forms an image on a recording material using developer(hereinafter referred to as “toner”). Examples of the image formingapparatus include a copier, a printer (a laser beam printer, a LEDprinter, or the like), a facsimile machine, a word processor, and amulti-function printer.

For the configuration and operation of a developing unit (or adeveloping apparatus) or a process cartridge, the terms such as “upper”,“lower”, “vertical”, and “horizontal” as used herein to representdirections refer to directions of the developing unit or the processcartridge as viewed during normal use thereof, unless otherwisespecified. In other words, the normal use of the developing unit(developing apparatus) or the process cartridge is a state where thedeveloping unit (developing apparatus) or the process cartridge isproperly installed in the properly arranged image forming apparatus mainbody so as to be used for an image forming operation.

[Image Forming Apparatus]

FIG. 1 is a schematic sectional view depicting a general configurationof an image forming apparatus 100 according to the present embodiment.The image forming apparatus 100 in the present embodiment is afull-color laser printer adopting an in-line system and an intermediatetransfer system. The image forming apparatus 100 can form a full-colorimage on a recording material (for example, a recording sheet, a plasticsheet, or a cloth) in accordance with image information. The imageinformation is input to an image forming apparatus main body 100Athrough host equipment such as an image reading apparatus connected tothe image forming apparatus main body 100A or a personal computer thatis connected to, and capable of communicating with, the image formingapparatus main body 100A.

The image forming apparatus 100 has, as a plurality of image formingsections, a first image forming portion SY, a second image formingportion SM, a third image forming portion SC, and a fourth image formingportion SK configured to form images in yellow (Y), magenta (M), cyan(C), and black (K), respectively. In the present embodiment, the firstto fourth image forming sections SY, SM, SC, and SK are arranged in linein a direction crossing the vertical direction. In the presentembodiment, the first to fourth image forming sections SY, SM, SC, andSK have the same configuration and perform the same operation except forthe color of an image formed by each image forming portion. The imageforming sections will be comprehensively described by omitting thesuffixes Y, M, C, and K added to the reference character in order toindicate for which of the colors the corresponding element is provided,unless the image forming sections need to be distinguished from oneanother. Of course, image forming sections with different sizes orshapes may be provided in the image forming apparatus depending on theconfiguration thereof.

The image forming apparatus 100 has four drum-shaped electrophotographicphotosensitive members juxtaposed in a direction crossing the verticaldirection, that is, photosensitive drums 1. The photosensitive drums 1are rotationally driven in a direction of arrow A (clockwise) by drivingmeans (driving source) not depicted in the drawings. Around each of thephotosensitive drums 1, a charging roller 2 is arranged which serves ascharging means for uniformly charging a surface of the photosensitivedrum 1, and a scanner unit (exposure apparatus) 3 is also arranged whichserves as exposure means for forming an electrostatic image(electrostatic latent image) on the photosensitive drum 1 by irradiationwith laser light based on image information. Around each of thephotosensitive drums 1, a developing unit (developing apparatus) 4 isarranged which serves as developing means for developing anelectrostatic image into a toner image, and a cleaning member 6 is alsoarranged which serves as cleaning means for removing toner(untransferred toner) remaining on the surface of the photosensitivedrum 1 after transfer. Opposite to the four photosensitive drums 1, anintermediate transfer belt 5 is arranged which serves as an intermediatetransfer member configured to transfer a toner image (developer image)on the photosensitive drum 1 to a recording material 12.

In the present embodiment, the developing unit 4 uses nonmagneticone-component developer toner as developer. In the present embodiment,the developing unit 4 performs reversal development by bringing adeveloping roller (described below) serving as a developer bearingmember into contact with the photosensitive drum 1. That is, in thepresent embodiment, the developing unit 4 develops an electrostaticimage by attaching toner charged with the same polarity (in the presentembodiment, a negative polarity) as that to which the photosensitivedrum 1 is charged, to a portion (an image portion or an exposed portion)of the photosensitive drum 1 on which charge has been attenuated byexposure.

In the present embodiment, the photosensitive drum 1, and the chargingroller 2, the developing unit 4, and the cleaning member 6, which serveas process means acting on the photosensitive drum 1, are integratedtogether, that is, integrated into a process cartridge 7. The processcartridge 7 can be installed in and removed from the image formingapparatus 100 via installation means such as an installation guide and apositioning member provided in the image forming apparatus main body100A. In the present embodiment, process cartridges 7 for the respectivecolors all have the same shape and store toner in yellow (Y), magenta(M), cyan (C), and black (K), respectively.

The intermediate transfer belt 5 formed using an endless belt andserving as an intermediate transfer member contacts all thephotosensitive drums 1 and moves (rotates) cyclically in the directionof arrow B (counterclockwise) in FIG. 1. The intermediate transfer belt5 is passed around a driver roller 51, a secondary transfer oppositeroller 52, and a driven roller 53 that serve as a plurality of supportmembers.

On an inner peripheral side of the intermediate transfer belt 5, fourprimary transfer rollers 8 are juxtaposed opposite the respectivephotosensitive drums 1 as primary transfer means. Each of the primarytransfer rollers 8 presses the intermediate transfer belt 5 toward thecorresponding photosensitive drum 1 to form a primary transfer portionN1 where the intermediate transfer belt 5 and the photosensitive drum 1contact each other. A bias with a polarity opposite to the regularcharging polarity of toner is applied to the primary transfer roller 8by a primary transfer bias power supply (high-voltage power supply)serving as primary transfer bias applying means and not depicted in thedrawings. Consequently, a toner image on the photosensitive drum 1 is(primarily) transferred onto the intermediate transfer belt 5.

At an outer peripheral side of the intermediate transfer belt 5, asecondary transfer roller 9 serving as secondary transfer means isarranged opposite the secondary transfer opposite roller 52. Thesecondary transfer roller 9 is compressed against the secondary transferopposite roller 52 via the intermediate transfer belt 5 to form asecondary transfer portion N2 where the intermediate transfer belt 5 andthe secondary transfer roller 9 contact each other. A bias with apolarity opposite to the regular charging polarity of toner is appliedto the secondary transfer roller 9 by a secondary transfer bias powersupply (high-voltage power supply) serving as secondary transfer biasapplying means and not depicted in the drawings. Consequently, a tonerimage on the intermediate transfer belt 5 is (secondarily) transferredonto the recording material 12.

At the time of image formation, first, the surface of the photosensitivedrum 1 is uniformly charged by the charging roller 2. Then, the surfaceof the charged photosensitive drum 1 is subjected to scanning exposurewith laser light emitted from the scanner unit 3, the laser light beingis association with image information, to form an electrostatic image onthe photosensitive drum 1 in accordance with the image information.Then, the electrostatic image formed on the photosensitive drum 1 isdeveloped into a toner image by the developing unit 4. The toner imageformed on the photosensitive drum 1 is (primarily) transferred onto theintermediate transfer belt 5 by action of the primary transfer roller 8.For example, when a full-color image is formed, the above-describedprocess is sequentially executed on the first to fourth image formingsections SY, SM, SC, and SK. Toner images in the respective images areprimarily transferred onto the intermediate transfer belt 5 in asuperimposed manner.

Subsequently, the recording material 12 is conveyed to the secondarytransfer portion N2 in synchronism with movement of the intermediatetransfer belt 5. The four-color toner images on the intermediatetransfer belt 5 are, in collective fashion, secondarily transferred ontothe recording material 12 by action of the secondary transfer roller 9,which is in contact with the intermediate transfer belt 5 via therecording material 12. The recording material 12 with the toner imagestransferred thereto is conveyed to a fixing apparatus 10 serving asfixing means. The fixing apparatus 10 heats and pressurizes therecording material 12 to fix the toner images to the recording material12.

Primarily untransferred toner remaining on the photosensitive drum 1after the primary transfer step is removed and collected by the cleaningmember 6. Secondarily untransferred toner remaining on the intermediatetransfer belt 5 after the secondary transfer step is cleaned by anintermediate transfer belt cleaning apparatus 11. Note that the imageforming apparatus 100 can also form monochromatic or multicolor imagesby using one desired piece of image forming sections singly or by usingonly a part (not all) of the image forming sections.

[Process Cartridge]

With reference to FIG. 2, a general configuration of the processcartridge 7, which is installed in the image forming apparatus 100, willbe described. FIG. 2 is a schematic (principal) sectional view of theprocess cartridge 7 in the present embodiment as viewed along alongitudinal direction (direction of a rotation axis) of thephotosensitive drum 1. In the present embodiment, the process cartridges7 for the respective colors have substantially the same configurationand perform substantially the same operation except for the type (color)of the developer stored in the process cartridge 7. The processcartridge 7 includes a photosensitive member unit 13 including thephotosensitive drum 1 and the developing unit 4 including a developingroller 17; the photosensitive member unit 13 and the developing unit 4are integrated together.

The photosensitive member unit 13 has a cleaning frame member 14 thatsupports the various elements in the photosensitive member unit 13. Thephotosensitive drum 1 is rotatably attached to the cleaning frame member14 via a bearing not depicted in the drawings. The photosensitive drum 1is rotationally driven in the direction of arrow A in FIG. 2 (clockwise)in accordance with an image forming operation by transmission, to thephotosensitive member unit 13, of a driving force of a driving motorserving as driving means (driving source) not depicted in the drawings.In the present embodiment, the photosensitive drum 1, which plays amajor role in an image forming process, is an organic photosensitivedrum 1 that is an aluminum cylinder coated with an undercoat layer thatis a functional film, a carrier generation layer, and a carrier transferlayer in this order on an outer peripheral surface thereof.

In the photosensitive member unit 13, the cleaning member 6 and thecharging roller 2 are arranged in contact with a peripheral surface ofthe photosensitive drum 1. The untransferred toner removed from thesurface of the photosensitive drum 1 by the cleaning member 6 falls intothe cleaning frame member 14, where the toner is stored (cleaningportion).

The charging roller 2, which is charging means, is rotationally drivenby bringing a conductive-rubber roller portion of the charging roller 2into contact with the photosensitive drum 1 under pressure. In acharging step, a predetermined DC voltage is applied to a cored bar ofthe charging roller 2 with respect to the photosensitive drum 1.Consequently, a uniform dark part potential (Vd) is formed on thesurface of the photosensitive drum 1. A spot pattern of laser light fromthe above-described scanner unit 3 in association with image dataexposes the photosensitive drum 1. In an exposed segment, carriers fromthe carrier generation layer eliminate the charge from the surface toreduce the potential. As a result, on the photosensitive drum 1, anelectrostatic latent image with a predetermined bright part potential(Vl) is formed in the exposed segment, and an electrostatic latent imagewith a predetermined dark part potential (Vd) is formed in an unexposedsegment. In the present embodiment, Vd=−520 V and Vl=−100 V.

The developing unit 4 has a developing chamber where the developingroller 17 and a toner supply roller 20 are arranged; the developingroller 17 serves as a developer bearing member configured to beardeveloper (toner) 80 and the toner supply roller 20 serving as adeveloper supply member that supplies toner to the developing roller 17.The developing unit 4 further includes a developer storage chamber, thatis, a toner storage chamber 18 (developer storage portion) arrangedbelow the toner supply roller 20 in the direction of gravity andcommunicating with the developing chamber through a developing opening33 and storing the toner 80. The toner supply roller 20 rotates incontact with the developing roller 17 via a nip portion N.

In the toner storage chamber 18, a stirring and conveying member 22 isprovided which stirs the toner in the toner storage chamber 18 and whichconveys the toner in the direction of arrow G in FIG. 2 toward an areaover the toner supply roller 20 denoted by V.

The present embodiment uses the developing blade as a regulating memberthat regulates the amount of the developer on the developer bearingmember.

The developing blade 21 is arranged under the developing roller 17 andcontacts the developing roller 17 in a counter direction to regulate thecoating amount of the toner supplied by the toner supply roller 20 andto apply charge to the toner. In the present embodiment, aleaf-spring-like thin plate formed of SUS and having a thickness of 0.1mm is used as the developing blade 21, and the spring elasticity of thethin plate is utilized to exert contact pressure. A surface of thedeveloping blade 21 is brought into contact with the toner and thedeveloping roller 17. The developing blade is not limited to this butmay be a thin metal plate such as phosphor bronze or aluminum.Furthermore, the surface of the developing blade 21 may be coated with athin film of a polyamide elastomer, urethane rubber, or a urethaneresin. The toner is provided with charge by triboelectric chargingresulting from rubbing between the developing blade 21 and thedeveloping roller 17 while being simultaneously regulated for layerthickness. In the present embodiment, a blade bias power supply notdepicted in the drawings applies a predetermined voltage to thedeveloping blade 21 to stabilize the toner coating. In the presentembodiment, a blade bias V of −400 V is applied.

The developing roller 17 and the photosensitive drum 1 rotate such that,in an opposite portion (contact portion), the surfaces of the developingroller 17 and the photosensitive drum 1 move in the same direction (inthe present embodiment, an upward direction). In the present embodiment,the developing roller 17 is arranged in contact with the photosensitivedrum 1. However, the developing roller 17 may be arranged in proximityto and at a predetermined distance from the photosensitive drum 1. Inthe present embodiment, the toner triboelectrically charged with thenegative polarity with respect to the predetermined DC bias applied tothe developing roller 17 by the bias power supply 17 c is transferred,due to this potential difference, only to the bright potential part ofthe development portion where the toner comes into contact with thephotosensitive drum 1, thus visualizing the electrostatic latent image.In the present embodiment, a voltage V of −300 V is applied to thedeveloping roller to generate a potential difference from the brightpotential part ΔV of 200 V, thus forming a toner image.

The toner supply roller 20 is disposed to form the predetermined contactportion (nip portion) N in the opposite portion on a peripheral surfaceof the developing roller 17. The toner supply roller 20 rotates in thedirection of arrow E in FIG. 2 (clockwise). The toner supply roller 20is an elastic sponge roller including a conductive cored bar with afoaming member layer formed on an outer peripheral surface thereof. Thetoner supply roller 20 and the developing roller 17 are in contact witheach other at a predetermined penetration level, that is, such that thetoner supply roller 20 is concaved by the developing roller 17 in aconcave amount ΔE, in FIG. 2. The toner supply roller 20 and thedeveloping roller 17 rotate in the contact portion N at differentperipheral speeds in the same direction. This operation allows the tonersupply roller 20 to supply toner to the developing roller 17. At thistime, the amount of the toner supplied to the developing roller 17 canbe adjusted by regulating the potential of the toner supply roller 20 soas to set an appropriate difference in potential between the tonersupply roller 20 and the developing roller 17. In the presentembodiment, the toner supply roller 20 and the developing roller 17 aredriven to rotate at 200 rpm and at 100 rpm, respectively, and the DCbias is applied such that the potential V of the developing roller 17 is+50 V with respect to the potential of the toner supply roller 20.

The developing roller 17 and the toner supply roller 20 in the presentembodiment both have an outside diameter of 15 mm. The penetration levelat which the toner supply roller 20 penetrates the developing roller 17is set to 1.0 mm, that is, the concave amount ΔE in which the tonersupply roller 20 is concaved by the developing roller 17 is set to 1.0mm. The toner supply roller 20 and the developing roller 17 are arrangedso as to have the same central height. The toner supply roller 20 usedin the present embodiment includes a conductive support member and afoaming member supported by the conductive support member. Specifically,the toner supply roller 20 is provided with a cored bar electrode 20 aserving as the conductive support member and having an outside diameterϕ5 (mm) and a urethane foam layer 20 b located around the cored barelectrode 20 a and serving as the foaming layer and containing opencells connected together. The toner supply roller 20 rotates in thedirection of arrow E in FIG. 2. Since the urethane in the front layercontains open cells, a large amount of the toner can enter the inside ofthe toner supply roller 20. The toner supply roller 20 in the presentembodiment offers a resistance of 1×10⁹ (Ω). As described below, thesurface of the developing roller in an unused state is coated with alubricant coating agent.

A method for measuring the resistance of the toner supply roller 20 willbe described. The toner supply roller 20 is brought into contact with analuminum sleeve with a diameter of 30 mm at a penetration level,described below, of 1.5 mm. The aluminum sleeve is rotated to rotate thetoner supply roller 20 at 30 rpm in conjunction with rotation of thealuminum sleeve. Then, a DC voltage of −50 V is applied to the aluminumsleeve. In this case, a resistor of 10 kΩ is provided on a ground side,and the resistance of the toner supply roller 20 is calculated bymeasuring the potential at each of the opposite ends of the resistor andcalculating a current from the voltages. In the present embodiment, thetoner supply roller 20 has a surface cell diameter of 50 μm to 1000 μm.

The cell diameter as used herein refers to the average diameter offoaming cells in any section. First, the area of the largest foamingcell is measured based on an enlarged image of any section, and aperfect-circle-equivalent diameter is calculated from the resultant areato obtain the maximum cell diameter. Then, foaming cells with a diameterequal to or smaller than half the maximum cell diameter are consideredto be noise and removed, and individual cell diameters are similarlycalculated from the cell areas of the remaining individual cells. Theaverage value of the resultant cell diameters is referred to as the celldiameter.

Subsequently, circulation of the toner in the developing chamber in acase where the toner supply roller 20 rotates in the direction of arrowE in FIG. 2 will be described. First, the toner stored in the tonerstorage portion 18 is thrown up by the toner conveying member 22 andmostly conveyed onto the supply roller 20. The toner conveyed to thesupply roller 20 remains on the surface of the supply roller 20 andinside the supply roller 20. The supply roller 20 then rotates in thedirection of arrow E in FIG. 2 to convey the toner to a positionimmediately before the nip between the supply roller 20 and thedeveloping roller 17. A portion of the supply roller 20 on which thetoner is conveyed is then deformed at the position immediately beforethe nip between the supply roller 20 and the developing roller 17. Thedeformation causes discharging of the toner remaining on the surface ofthe supply roller 20 and inside the supply roller 20. The dischargedtoner is stored in a space (hereinafter referred to as a “temporarytoner storage portion V”) over the developing roller 17 and the supplyroller 20.

A portion of the toner stored in the temporary toner storage portion Vis blown into the nip portion N as a result of the rotation of thedeveloping roller 17 and the supply roller 20. The toner blown into thenip portion N is charged due to the rubbing between the developingroller 17 and the supply roller 20. Upon passing through the nip portionN, the charged toner is electrostatically stuck to the developing roller17 due to an amount of charge in the toner. This effect allows the tonerto be fed from the supply roller 20 to the developing roller 17. Aportion of the toner fed to the developing roller 17 is regulated by thedeveloping blade 21, which is a developer regulating member, to form atoner coat with a desired layer thickness over the developing roller 17.The regulated toner falls by gravity to return to the toner storageportion 18.

As described above, the toner stored in the temporary toner storageportion V is fed to the developing roller 17 to form a toner coat. Inother words, stable formation of a toner coat needs a configuration thatcontinues to supply a desired amount of the toner to the temporary tonerstorage portion V.

[Coating Agent]

Now, a coating agent applied to the developing roller 17 in the presentembodiment will be described in detail. Powder other than the toner isused for the developing roller 17 in the present embodiment in order toprotect the developing roller 17 from the time of manufacture until auser starts to use the developing roller 17 and to allow the powder tofunction as a lubricant for the developing blade 21 when the developingblade 21 starts to be used. Approximately 10 to 150 mg of the coatingagent is applied to the developing roller 17. In the present embodiment,the powder used as the coating agent 22 is Tospearl (trade name)manufactured by Momentive Performance Materials Inc (formerly ToshibaSilicone Co., Ltd.). The coating agent 22 is 2 μm in average particlesize. The coating agent 22 adopted in the present embodiment ischaracterized by having higher charge than the toner used fordevelopment. Specifically, in an environment at a temperature of 23° C.and a humidity of 40%, compared to the toner, which has an initialaverage charge of approximately 50 μC/g per unit mass, Tospearl has anaverage charge of 90 μC/g per unit mass. Any known developer may be usedas needed so long as the developer is a nonmagnetic one-componentdeveloper having lower charging characteristics than the coating agentas described above. The developer preferably has a larger averageparticle size than the coating agent.

The present embodiment uses Tospearl with a particle size of 2 μm.However, the present invention is not limited to this. Any coating agentmay be used as needed so long as the coating agent functions withoutcausing the developing blade 21 to be curled back. Specifically,materials and particle sizes described below are used for the coatingagent 22 in view of the electrical characteristics thereof exhibitedwith respect to the developing roller 17 and the developing blade 21.Examples of the material include a urethane resin, a silicone resin, apolyester resin, a styrene resin, an acrylic resin, a styrene-acrylicresin, or a blend resin thereof. A charge control agent, a wax, and thelike are kneaded into any of these resins, which is then pulverized by aknown pulverization method to form matrix particles. Alternatively, anexternal additive may be applied. For the particle size, a combinationof materials is possible, as appropriate, within the range from 0.8 μmto 10 μm.

[Filling Amount of the Developer]

With reference to FIGS. 3A to 3C, the amount of the developer placed inthe developing apparatus 4 in the present embodiment will be describedin detail. For the developing apparatus 4, three different levels areavailable for the filling amount of the toner. That is, in the imageforming apparatus according to the present embodiment, three types ofdeveloping apparatuses 4 including toner chambers having differentfilling amounts of toner in an unused state (initial state) are eachconfigured so that the developing apparatus 4 can be installed in andremoved from the apparatus main body 100A. FIGS. 3A to 3C are schematicsectional views of the developing apparatus 4 in the present embodiment.FIG. 3A depicts a developing apparatus 4 of a type having an initialfilling amount of 240 g. FIG. 3B depicts a developing apparatus 4 of atype having an initial filling amount of 150 g. FIG. 3C depicts adeveloping apparatus 4 of a type having an initial filling amount of 100g. The user can select one of the three types of the developingapparatus 4 to be installed in the apparatus main body 100A according touse frequency and costs. This provides an appropriate degree of freedom.

Information on the filling amount for the developing apparatus 4 isstored in a nonvolatile memory 200 as information specific to thedeveloping apparatus. The nonvolatile memory 200 is, for example, arewritable flash ROM that stores a system program configured to controlthe image forming apparatus, the number of recording sheets with imagesrecorded thereon, information on the life of the developing apparatus,information on the remaining amount of the toner, various adjustmentvalues, and the like. The nonvolatile memory 200 also stores, forexample, system data indicative of the serial number and the productiondate of the apparatus. The nonvolatile memory 200 stores, in addition tothe above-described information, information on the filing amount forthe developing apparatus as information specific to the developingapparatus.

In the present embodiment, the information on the filling amount of thetoner is based on the filling amounts held in the nonvolatile ROM.However, information used to determine the filling amount is not limitedto this. Any of the following pieces of information may be used insteadso long as the information allows a difference in the filling amount ofthe toner to be determined: the nominal life of the developing apparatusand the number of sheets that can be printed by the developingapparatus, the lifetime limit number of rotations of the developingroller, the amount of toner available, or the lifetime limit number ofrotations of the corresponding photosensitive drum. The presentembodiment uses the information on the filling amount of the developer,but the nonvolatile memory 200 may hold information on the amount of thedeveloper stored in the developing apparatus in the unused state (newdeveloping apparatus).

[Filling Amount Detecting Means]

A CPU 100B (FIG. 2) is arranged in the image forming apparatus as acentral processing unit. The CPU is a control portion that reads thevarious adjustment values from the nonvolatile memory mounted in thedeveloping apparatus to control the image forming apparatus. The CPUdetects, in the nonvolatile memory, the information on the initialfilling amount for the developing apparatus and selects one of thedischarge control programs predetermined for the respective fillingamounts. The selected discharge control program then performs control.In the present embodiment, the filling amount of the toner in thedeveloping apparatus is determined based on the information in thenonvolatile memory. However, the present invention is not limited tothis. The filling amount of the toner may be detected as needed by, forexample, changing a container shape (for example, a rib) for thedeveloping apparatus according to the filling amount of the toner andallowing the image forming apparatus to detect a difference in containershape.

[Discharge Control]

Now, control for discharge of the coating agent in the presentembodiment will be described in detail. The coating agent applied to thedeveloping roller 17 during the initial period of use of the developingapparatus is mostly collected on the surface of the toner supply roller20 and inside the toner supply roller 20 due to rotation rubbing betweenthe developing roller 17 and the supply roller 20.

Since the coating agent in the present embodiment is characterized byhaving higher charge than the toner, the discharge control needs to beperformed at potential settings different from potential settings fornormal image formation. That is, a potential difference is caused whichhas a polarity opposite to the polarity with which the coating agent ischarged by the developing blade 21; the potential difference has alarger absolute value than a potential difference resulting from animage forming operation. Specifically, a DC bias is applied to the tonersupply roller 20 by a bias power supply 20 c and to the developingroller 17 by a bias power supply 17 c such that the developing roller 17has a potential V of +300 V with respect to the potential of the tonersupply roller 20. The bias power supplies 20 c and 17 c and the CPU100B, which controls the application of the bias to the toner supplyroller 20 and the developing roller 17, correspond to a voltage applyingportion in the present invention. Since Tospearl, which is used as thecoating agent in the present embodiment, has higher chargingcharacteristics than the toner in the toner storage chamber 18, thecoating agent is electrostatically fed to the developing roller 17,which has an apparently positive potential. In this manner, thepotential settings based on the electrical characteristics of thecoating agent enable the coating agent remaining in the toner supplyroller 20 to be actively fed to the developing roller 17.

When subjected to a solid-black-image forming operation corresponding toone circumference of the developing roller 17 along with the toner, thecoating agent thus collected in the developing roller 17 moves to thephotosensitive drum 1 along with the toner and collected in a cleanercontainer. This operation enables a reliable reduction in the amount ofcoating agent remaining in the developing chamber. The discharge controlalso supplies the lubricant to the cleaning member 6. At this time, theintermediate transfer belt 5 and the photosensitive drum 1 are separatefrom each other, and thus the toner moved from the developing apparatus4 to the photosensitive drum 1 is all collected in the cleaning member6.

The present embodiment sets the above-described potentials because ofthe use of the coating agent having higher charging characteristics thanthe toner. However, the present invention is not limited to this. Thepotentials may be set so as to allow efficient discharge to be achievedin accordance with the electrical characteristics of the coating agent.

[Toner Discharge Control Flow]

Toner discharge control in Embodiment 1 will be described with referenceto FIG. 4. FIG. 4 illustrates a flowchart of a discharging operation inEmbodiment 1. In the present embodiment, as described above, the CPU inthe image forming apparatus switches an operational condition for thedischarging operation between (4) t4 and (12) t11 and (15) t13 inaccordance with the initial-filling-amount information in thenonvolatile memory. In particular, the present embodiment ischaracterized in that the control program for the discharging operationallows the coating agent to be more actively discharged for thedeveloping apparatus with a smaller filling amount. In the presentembodiment, the predetermined count number of sheets printed is used asa discharge frequency, and the developing apparatus with a smallerfilling amount starts to undergo the discharge control at a smallerprint count number than the developing apparatus with a larger fillingamount.

In the present embodiment, the CPU 100B also functions as a storageamount detecting portion that detects the initial filling amount of thedeveloper toner (storage amount), a discharge control portion thatchanges the execution frequency for the discharging operation(operational condition), a count portion that counts the number ofexecutions of the image forming operation, a life detecting portion, aremaining amount detecting portion, and the like.

(1) The filling amount detecting means allows the image formingapparatus to detect the filing amount of the toner in the developingapparatus (t1).

(2) The detection result indicates that the filling amount is 100 g(t2).

(3) The detection result indicative of 100 g is transmitted to tonerdischarge control means (t3).

(4) Detection means selects a discharge frequency of 100 sheetscorresponding to a filling amount of 100 g (t4).

(5) Normal image formation is performed (t5).

(6) A count in a counter is incremented each time an image is formed(t6).

(7) A given number of sheets are fed and then count in the counterreaches the predetermined count number (t7).

(8) The discharge control means detects the arrival of the sheets at thecounter to perform the discharging operation (t8).

(9) Once the discharging operation is ended, the counter is reset tozero (t9).

(10) The process subsequently returns to (t5) and loops from (t5) to(t9).

(11) At (t2), a detection result indicative of 150 g is transmitted tothe toner discharge control means (t10).

(12) The detection means selects a discharge frequency of 300 sheetscorresponding to a filling amount of 150 g (t11).

(13) As is the case with 100 g, the process subsequently loops from (t5)to (t9).

(14) At (t2), a detection result indicative of 240 g is transmitted tothe toner discharge control means (t12).

(15) The detection means selects a discharge frequency of 600 sheetscorresponding to a filling amount of 240 g (t13).

(16) As is the case with 100 g, the process subsequently loops from (t5)to (t9).

<Comparative Verification>

The configuration in the embodiment of the present invention wasverified using the present embodiment and comparative examples describedbelow in order to verify the effect of the discharging performance forthe coating agent. The filling amount of toner in a developing devicewas 150 g.

Embodiment 1

Embodiment 1 of the present invention is a configuration that performsthe operation during the discharge in the above-described embodiment andthe discharge control flow (FIG. 4). In Embodiment 1, the dischargecontrol program in the CPU in the image forming apparatus sets thepredetermined count number of sheets printed to be the dischargefrequency. The developing apparatus with a smaller filling amount startsto undergo the discharge control at smaller print intervals than thedeveloping apparatus with a larger filling amount.

Comparative Example 1; Related Art

In Comparative Example 1, during low-printing intermittent durabilitytests, the toner is sequentially discharged so as to achieve apredetermined printing rate as described above in the BACKGROUND OF THEINVENTION. In the present comparative example, the toner dischargingoperation is controllably performed as needed so as to achieve aprinting rate of 5%.

Comparative Example 2; Related Art

In Comparative Example 2, the potential settings for execution of thedischarge control are the same as the potential settings for the normalimage formation. The frequency and the discharge amount are similar tothe frequency and the discharge amount in Embodiment 1. The fillingamount of the toner is 150 g.

Embodiment 2

FIG. 5 illustrates a discharge control flow for Embodiment 2 of thepresent invention. In Embodiment 2, the discharge control program in theCPU in the image forming apparatus sets the frequency (operationalcondition) such that the discharging operation is performed each time adevelopment life held in the nonvolatile memory decreases by apredetermined percentage, and varies the frequency (operationalcondition) according to the filling amount. That is, for the largestfilling amount of 240 g, the discharging operation is performed eachtime the development life decreases by 3% (t16). For the smallestfilling amount of 100 g, the discharging operation is performed eachtime the development life decreases by 1% (t14). For an intermediatefilling amount of 150 g between the largest and smallest fillingamounts, the discharging operation is performed each time thedevelopment life decreases by 2% (t15). The development life as usedherein refers to the rate of the remaining life based on the number ofrotations of the developing roller. The remaining part of theconfiguration is similar to the configuration in Embodiment 1.

Embodiment 3

FIG. 6 illustrates a discharge control flow for Embodiment 3 of thepresent invention. In Embodiment 3, the discharge control program in theCPU in the image forming apparatus sets the frequency (operationalcondition) such that the discharging operation is performed each timethe remaining percentage of toner held in the nonvolatile memorydecreases by a predetermined percentage, and varies the frequency(operational condition) according to the filling amount. That is, forthe largest filling amount of 240 g, the discharging operation isperformed each time the remaining percentage of toner decreases by 3%(t19). For the smallest filling amount of 100 g, the dischargingoperation is performed each time the remaining percentage of tonerdecreases by 1% (t17). For an intermediate filling amount of 150 gbetween the largest and smallest filling amounts, the dischargingoperation is performed each time the remaining percentage of tonerdecreases by 2% (t18). The remaining part of the configuration issimilar to the configuration in Embodiment 1.

Embodiment 4

FIG. 7 illustrates a discharge control flow for Embodiment 4 of thepresent invention. In Embodiment 4, the discharge control program in theCPU in the image forming apparatus performs the discharge control byvarying the discharge amount during discharge (operational condition)according to the filling amount. That is, for the largest filling amountof 240 g, the discharge amount during discharge (operational condition)is such that the discharging operation is performed each time thedeveloping roller (D roller) rotates a distance equal to twocircumferences thereof (t22). For the smallest filling amount of 100 g,the discharging operation is performed each time the developing roller(D roller) rotates a distance equal to 10 circumferences thereof (t20).For an intermediate filling amount of 150 g between the largest andsmallest filling amounts, the discharging operation is performed eachtime the developing roller rotates a distance equal to fivecircumferences thereof (t21). The discharge frequency is such that thedischarging operation is performed each time 500 printed and fed sheetsare counted regardless of the initial filling amount. The remaining partof the configuration is similar to the configuration in Embodiment 1.

<Verification 1: Relation between the Residual Concentration of theCoating Agent and Streaks>

To confirm the effect of discharging performance for the coating agent,low-printing intermittent durability tests were conducted on thedeveloping apparatuses using the discharging method in theabove-described comparative example to check whether or not an abnormalimage was generated.

[Method]

In an environment at a temperature of 15° C. and a humidity of 10%,image formation was performed at a low printing rate at intervals of twosheets using the image forming apparatus in the present embodiment.Images were periodically checked to determine whether an abnormal imagewas generated. Durability evaluation was performed on using a new cyantoner in the unused state, and the initial filling amount of the tonerwas 150 g. The amount of coating agent applied to the developing rollerwas set to 50 mg for all of the developing apparatus.

[Results]

Table 1-1 in FIG. 8 illustrates the results of the present verification.A state where no streaks are generated on the images is denoted by A inthe table. A state where streaks on the images have a length of lessthan 2 cm is denoted by B in the table. A state where streaks on theimages have a length of 2 cm or more is denoted by C in the table. Theresults indicate that all of Embodiments 1 to 4 successfully suppressedgeneration of an abnormal image. This will be described below in detail.

<Verification 2: Verification of the Discharging Performance>

The developing apparatus used for the durability tests in Verification 1was used to rotationally drive the developing roller. Whether thecoating agent (Tospearl) was developed on the developing roller (whetherthe peeled-off coating agent was attached to the developing rolleragain) was visually checked.

[Method]

In an environment at a temperature of 15° C. and a humidity of 10%, thedeveloping apparatuses used in Verification 1 were used and theremaining amount of the toner resulting from the durability tests wasset to 30 g for all of the developing apparatuses. The developing rollerwas rotated for development with no toner consumed. The state of thecoat on the developing roller was visually checked to determine whetherTospearl was developed. The potential settings for the driving fordevelopment were equal to the potential settings for the dischargingoperation. The state of the toner coat on the developing roller afterone-minute driving was checked.

[Results]

Table 1-2 in FIG. 8 illustrates the results of the present verification.Circles “◯” in the table indicate the absence of the coating agent onthe developing roller. Crosses “X” in the table indicate that thepresence of the coating agent on the developing roller was confirmed.Embodiments 1 to 4 produced favorable results indicating that no coatingagent was coated on the developing rollers. This will be described belowin detail.

<Verification 3: Verification of the Discharging Performance>

The same examinations as those in Verification 2 were executed. That is,the developing roller was rotationally driven with no toner consumed.Whether the coating agent coated on the developing roller was visuallychecked.

[Method]

In an environment at a temperature of 15° C. and a humidity of 10%, thedeveloping apparatuses filled with 30 g of new toner were prepared, andthe developing roller was rotated for development with no tonerconsumed. The state of the coat on the developing roller was visuallychecked to determine whether Tospearl was developed. The potentialsettings for the driving for development were equal to the potentialsettings for the discharging operation. The state of the toner coat onthe developing roller after one-minute driving was checked. The amountof the coating agent was 50 mg.

[Results]

Table 1-3 in FIG. 8 illustrates the results of the present verification.Circles “◯” in the table indicate the absence of the coating agent onthe developing roller. Crosses “X” in the table indicate that thepresence of the coating agent on the developing roller was confirmed.Even with the new toner, Embodiments 1 to 4 produced favorable resultsindicating that no coating agent was coated on the developing rollers.This will be described below in detail.

<Verification Results>

Advantages of Embodiments 1 to 4 of the present invention overComparative Example 1 will be described. The reason why abnormal imageswere generated in the configuration in Comparative Example 1 is expectedto relate to the results of Verification 2. That is, during the latterhalf of the durability tests, a large amount of coating agent waspresent in the developing chamber, resulting in the likelihood that thecoating agent was developed. Two causes are possible. First, the mannerof discharging the coating agent was problematic, and the coating agentwas actually likely to have failed to be discharged. Second, thedischarge frequency corresponding to a constant printing rate limits theamount of coating agent discharged at a time. This is expected to reducedischarge efficiency to cause streak images to be generated.

Advantages of the present invention over Comparative Example 2 will bedescribed. The potential control in Comparative Example 2 fails toefficiently discharge the coating agent, leading to a reduced dischargeefficiency for the coating agent. Thus, during the latter half of thedurability tests, the residual concentration of the coating agent isexpected to have increased to cause streak images to be generated.

The results of the verifications by the present inventors indicate thata high residual concentration of the coating agent causes the coatingagent to be developed on the developing roller. In particular, thistendency is significant when the toner is degraded.

With reference to FIG. 9 and FIG. 10, the results of verifications 2 and3 will further be verified. FIG. 9 is a graph illustrating the resultsof Verifications 2 and 3 in terms of the residual concentration of thecoating agent and the coat of the developer. FIG. 10 is a diagramillustrating the residual concentration of the coating agent and thecoat of the developer. Ranking on the axis of ordinate in the graph inFIG. 9 represents five ranks of the amount of coating agent developed onthe developing roller. The graph indicates that the amount of coatingagent developed on the developing roller decreases consistently with theresidual concentration of the coating agent. The graph also indicatesthat, even with the same residual concentration, the likelihood ofdevelopment of the coating agent varies depending on the degradationstatus of the toner. In particular, the toner with the durabilitythereof degraded tends to make the coating agent likely to be developed.This is because, as depicted in FIG. 10, degraded charging performanceof the toner makes the coating agent with high charging performancelikely to be coated on the developing roller.

Based on the above-described examinations, in Embodiments 1 to 4, thecoating agent is intermittently discharged to the outside of thedeveloping chamber so as to set the residual concentration of thecoating agent to less than 0.005%, at which generation of abnormalimages is prevented even with the toner with the durability thereofdegraded. To achieve such discharge, different discharge controlprograms are prepared for the respective initial weights and thedischarge control for the coating agent is performed using a methodoptimum for the initial weight. In Embodiments 1 to 4, abnormal imagesattributed to the coating agent can be suppressed by performing thedischarge control for the developing apparatus with a small fillingamount on the developing apparatus with a large filling amount of thetoner. However, the coating agent is discharged along with the toner,and thus, an increased discharge frequency for the developing apparatuswith a large filling amount of the toner undesirably reduces the amountof the toner that can be used for image formation by the user. Thus, inEmbodiments 1 to 4, the appropriate control is performed such that theoperational condition for the discharging operation is varied accordingto the filling amount of the toner in the developing apparatus to allowmaximization of the amount of the toner that can be used by the userwhile reducing possible abnormal images attributed to the residualcoating agent.

As described above, the developing apparatuses in Embodiments 1 to 4exhibited the lowest residual concentration of the coating agent afterthe durability tests. The results of the examinations by the inventorsindicate that the discharge efficiency can be increased by setting thepotentials optimum for discharge according to the electricalcharacteristics of the coating agent. For the developing apparatus witha smaller filling amount, the residual concentration of the coatingagent can be reduced by increasing the discharge frequency or thedischarge amount (varying the operational condition).

As described above, for a new developing apparatus in which thedeveloper bearing member is coated with powder other than the developerused for image formation, the present embodiment can effectively performcontrol that allows the coating agent to be reliably discharged to theoutside the developing chamber. Thus, even in a situation where thecharging characteristics of the toner are degraded as a result ofdeterioration of durability of the developer or degradation of thedeveloper bearing member, the amount of residual coating agent reliablydecreases, enabling a reduction in inappropriate images attributed tothe initially applied coating agent. Therefore, image formation can bestably achieved throughout the life of the developing apparatuses.

In the above-described embodiment, the image forming apparatus capableof forming color images is illustrated. However, the image formingapparatus to which the present invention can be applied is not limitedto this. Similar effects can be produced by an image forming apparatuscapable of forming monochromatic images. Similarly, the presentembodiment adopts the contact developing system using the nonmagneticone-component toner. However, the present invention is not limited tothis. Similar effects can be produced by adopting a jumping developingscheme.

In the above-described embodiment, operation of discharging the powderother than the developer depending on the filling amount of the toner inthe developing apparatus is controlled such that the amount of thedeveloper discharged per unit number of printed sheets is controllablyincreased for the developing apparatus with a smaller filling amount ofthe toner.

In other words, the discharging operation of discharging the powderother than the developer is controlled such that the first amount of thepowder discharged when the first amount of the developer is detected islarger than the second amount of the powder discharged when the secondamount of the developer that is larger than the first amount of thedeveloper is detected. In this case, means used is not particularlylimited, and for example, the amount of the powder discharged at a timemay be increased, or the number of times that the powder is dischargedmay be increased with the same amount of the powder discharged.

As a result, the amount of the developer discharged per unit number ofprinted sheets may be increased with decreasing initial content of thedeveloper.

Moreover, the present invention is not limited to the above-describedconfiguration. Any configuration may be used as needed so long as theconfiguration increases the amount of the developer discharged per unitnumber of printed sheets for the developing apparatus with a smallerfilling amount of the toner, in order to accomplish various purposessuch as suppression of degradation of the toner, stabilization ofcleaning performance of the photosensitive drum, and stabilization ofcleaning of the intermediate transfer member.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2015-121021, filed on Jun. 16, 2015, and Japanese Patent Application No.2016-100627, filed on May 19, 2016, which are hereby incorporated byreference herein in their entirety.

What is claimed is:
 1. An image forming apparatus comprising: an imagebearing member configured to bear a developer image; a developingapparatus having a developer bearing member that bears developer and aregulating member that regulates an amount of the developer on thedeveloper bearing member; an acquiring portion configured to acquire anamount information related to an amount of the developer stored in thedeveloping apparatus; and a control portion configured to perform adischarging operation for discharging the developer from the developingapparatus, apart from an image forming operation, wherein the developerbearing member bears a coating agent that is a powder other than thedeveloper during an unused state, and in the discharging operation, afirst amount of the developer is discharged when a first amountinformation, as the amount information, is acquired, and a second amountof the developer is discharged when a second amount information, as theamount of information, indicates a larger developer amount than thedeveloper amount indicated by the first amount of information, and thefirst amount of the developer discharged being larger than the secondamount of the developer discharged.
 2. The image forming apparatusaccording to claim 1, further comprising a voltage applying portionconfigured to apply, to the developer bearing member, a voltage causinga potential difference between the developer bearing member and a supplymember, wherein the voltage applying portion applies, during thedischarging operation, a voltage that causes a first potentialdifference with a magnitude different from a magnitude of a potentialdifference caused during the image forming operation, to the developerbearing member.
 3. The image forming apparatus according to claim 2,wherein the voltage applying portion applies, during the dischargingoperation, a voltage that causes the first potential difference having apolarity opposite to a charging polarity of the coating agent charged bythe regulating member and having a larger absolute value than a secondpotential difference caused during the image forming operation, to thedeveloper bearing member.
 4. The image forming apparatus according toclaim 1, further comprising a count portion configured to count a numberof executions of the image forming operation, wherein the dischargingoperation is executed when a count in the count portion reaches apredetermined value, and the control portion increases an executionfrequency of the discharging operation by reducing the predeterminedvalue consistently with a decreasing initial amount of the developerstored.
 5. The image forming apparatus according to claim 1, furthercomprising a life acquiring portion configured to acquire a rate of aremaining life of the developer bearing member or the image bearingmember, wherein the discharging operation is executed each time the rateof the remaining life acquired by the life acquiring portion decreasesby a predetermined percentage, and the control portion increases anexecution frequency of the discharging operation by reducing thepredetermined percentage consistently with a decreasing initial amountof the developer stored.
 6. The image forming apparatus according toclaim 5, wherein the remaining life is based on a number of rotations ofthe developer bearing member or the image bearing member.
 7. The imageforming apparatus according to claim 1, further comprising a remainingamount acquiring portion configured to acquire a ratio of a remainingamount of the developer to an initial amount of the developer stored,wherein the discharging operation is executed each time the ratio of theremaining amount acquired by the remaining amount acquiring portiondecreases by a predetermined percentage, and the control portionincreases an execution frequency of the discharging operation byreducing the predetermined percentage consistently with a decreasinginitial amount of the developer stored.
 8. The image forming apparatusaccording to claim 2, further comprising a count portion configured tocount a number of rotations of the developer bearing member, wherein thedischarging operation is executed when a count in the count portionreaches a predetermined value, and the control portion increases anexecution frequency of the discharging operation by reducing thepredetermined value consistently with a decreasing initial amount of thedeveloper stored.
 9. The image forming apparatus according to claim 1,further comprising a supply member that contacts the developer bearingmember to supply the developer to the developer bearing member.
 10. Theimage forming apparatus according to claim 1, wherein at least thedeveloper bearing member and the regulating member are integratedtogether into a cartridge and enabled to be installed in and removedfrom an apparatus main body of the image forming apparatus.
 11. Theimage forming apparatus according to claim 1, wherein the coating agenthas a smaller average particle size than the developer.
 12. The imageforming apparatus according to claim 1, wherein the amount informationshows a nominal life of the developing apparatus, the number of sheets,the lifetime limit number of rotations of a developing roller of thedeveloping apparatus, an amount of toner available, a shape of thedeveloping apparatus, or the lifetime limit number of rotations of theimage bearing member.
 13. The image forming apparatus according to claim1, wherein the acquiring portion acquires an initial amount informationof the developer as the amount information.
 14. An image formingapparatus comprising: an image bearing member configured to bear adeveloper image; a developing apparatus including a developer bearingmember that bears developer and a regulating member that regulates anamount of the developer borne by the developer bearing member and thatcharges the developer; and an acquisition portion configured to acquirean amount information related to an amount of the developer stored inthe developing apparatus, the image forming apparatus configured toexecute a discharging operation that is different from an image formingoperation of forming the developer image on a recording material and tomove the developer from the developer bearing member to the imagebearing member, wherein a coating agent that is a powder other than thedeveloper is applied to the developer bearing member during an unusedstate, and the image forming apparatus comprises a control portionconfigured to vary an execution frequency of the discharging operationso as to increase the execution frequency of the discharging operationwith respect to an execution frequency of the image forming operation asthe amount information of the developer acquired by the acquisitionportion indicates that the amount of the developer decreases.
 15. Theimage forming apparatus according to claim 14, wherein the acquisitionportion acquires an initial amount of the developer as the amountinformation.
 16. The image forming apparatus according to claim 14,wherein the amount information shows a nominal life of the developingapparatus, the number of sheets, the lifetime limit number of rotationsof a developing roller of the developing apparatus, an amount of toneravailable, a shape of the developing apparatus, or the lifetime limitnumber of rotations of the image bearing member.